Knife sharpener

ABSTRACT

A knife sharpener comprising a housing plate supporting a pair of sharpening rods that are curved to a specified dimension for maximizing the knife sharpener&#39;s ability to utilize and engage adjustable flexible bumper arms mounted on a positive stop that provides the sharpener&#39;s rods best angles and pressure for obtaining an even, consistent edge realignment, no matter what sharpening technique is used. Adjustable spring and cam mechanisms enable easy positioning of the initial, crossing-point of the sharpening rods over the center of a sharpening slot.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to knife sharpeners, and more particularly, to a knife sharpener that utilizes a pair of curved sharpening rods that engage and interact with an impact-absorbing flexible bumper arm assembly which controls and guides the sharpening rods to optimal angles and pressures that enhance obtaining even and consistent edge alignment of a knife regardless of what sharpening techniques are used.

[0002] Various blade or knife sharpening devices are known in the prior art that utilize a pair of sharpening rods that are pivotally mounted and cross one another over a slot which receives and guides the blade to be sharpened. Representative of this prior art are U.S. Pat. Nos. 5,478,272 and 5,655,959, the contents of which are incorporated by reference herein.

[0003] As described in the U.S. Pat. No. 5,4578,272 patent, the sharpening rods define a V-shaped intersection therebetween that overlies a knife guiding slot, with the V-shaped intersection point moving along the slot as the knife is pressed against the sharpening rods.

[0004] One drawback of the prior art is that at the point that the rods reach an end-of-motion stopper, continued pressing of the knife against the V-shaped intersection results in some loss of control over the precise angles at which the knife meets that sharpening rods.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide an improved knife sharpener.

[0006] It is another object of the present invention to provide a knife sharpener that is more durable and easier to use.

[0007] It is yet a further object of the present invention to provide a knife sharpener that utilizes a pair of curved sharpening rods that are controlled to provide optimal angles and pressures and which obtain even and consistent edge realignment and/or edge retrieval, regardless of the sharpening technique being employed by the particular person who sharpens the knife.

[0008] The foregoing and other objects of the invention are realized with a knife sharpening unit that supports on a housing plate a pair of sharpening rods that are curved to specific dimensions for maximizing the knife sharpener's ability to utilize and engage an impact-absorbing flexible bumper arm assembly. The flexible bumper arm assembly controls and guides the sharpening rods at their end-of-travel point, in a manner that alters the angle of intersection between the sharpening rods and the pressures applied to the blade of the knife to obtain even and consistent edge realignment.

[0009] Preferably, the sharpener is provided with markings on the housing plate that permit adjustment of the initial intersection point between the sharpening rods. Preferably, additional markings are provided to indicate to a user a “sweet spot” of the knife sharpening unit.

[0010] The pair of sharpening rods are resiliently biased to an initial position, defining an initial intersection, by a spring mechanism. In one embodiment, that mechanism is in the form of first and second leaf or plate springs, the free ends of which are fixed between pairs of cams that enable adjusting the location of the initial intersection point of the sharpening rods across the knife slot. Preferably, the mechanism comprises coiled springs. Another expedient uses torsion springs.

[0011] Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a back view of the knife sharpener of the present invention.

[0013]FIG. 2 is a side view of the knife sharpener of the present invention, as seen along lines 2-2 in FIG. 1.

[0014]FIG. 3 is a front view (partially in perspective) of the knife sharpener of the present invention.

[0015]FIG. 4 is a top view of the knife sharpener of the present invention, as seen along lines 4-4 of FIG. 3.

[0016]FIG. 5 shows a modified, front view of the knife sharpener of the present invention, including a tip enhancer device.

[0017]FIG. 6 shows a modified back view of the knife sharpener of the present invention, including an alternate spring mechanism for the sharpening rods.

[0018]FIG. 7 is a back view of the knife sharpener of the present invention, illustrating yet another spring mechanism for the sharpening rods.

[0019]FIG. 8 is perspective of the front of the knife sharpener of the present invention, illustrating the manner of its utilization.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0020] With reference to the drawings and primarily FIG. 1, the knife sharpener 10 of the present invention is comprised in the main of a housing plate 53 with two main sections 54 and 56 that are separated by a knife slot 60. The housing plate supports a pair of pivotally movable sharpening rods 12, 14 that are resiliently biased toward an initial position by spring arms 24, 30, the sharpening rods crossing one another at a movable V-shaped intersection point 13, the location of which moves along the slot 60, as a knife is pressed down the slot 60.

[0021] The housing plate 53 is preferably made of a solid, ½ inch thick UHMW and/or high-density polyethylene, durable, one-piece construction material. It has been designed so that the knife blade 77 (FIG. 8) will avoid cutting into the housing plate 53 during normal use. The blind high wall 55 (FIG. 8) on the right side of the housing plate 53 helps guide the blade 77 down into the sharpening slot 60 using minimal effort and skill.

[0022] Four adjustable upper and lower offset cams 26, 28 and 32, 34 elevate and lower the stainless steel spring arms 24, 30 to easily position the sharpening rods 12, 14 to the proper height and into the center of the sharpening slot. Proper cam adjustments also create the correct positive and negative force within the spring arms 24, 30 as to precisely generate the even, consistent flex tension necessary to keep the blade angles symmetrical for maximizing edge retrieval. Extra spring arms can also be stacked on top of one another to exert extra sharpening force if needed.

[0023] Each sharpening rod spring assembly is made of a combination of the following materials: a round, stainless steel sharpening rod 12, 14 and a flat stainless steel spring 24, 30. These two pieces are mounted onto a block of UHMW 16, 18, or stainless steel material.

[0024] The four adjustable upper and lower cams can easily position the sharpening rods 12, 14 into the center of the sharpening slot 60 by elevating or lowering the flat, stainless spring arm. Unlike other sharpeners, this new use of cams allows for adjustments to compensate for material fatigue, as well as proper angle setup adjustment specifications.

[0025] The rods 24, 30 are supported at their non-free ends in first and second respective blocks 16, 18 that are pivotally mounted by pivots 20, 22. Note further the alignment windows 36 and 38, which help an operator align the initial V-shaped intersection (crossing point) of the rods 12, 14 by adjusting the cams 26, 28 and 32, 34 by operating their center screws using an appropriate tool, for example, a screwdriver (not shown).

[0026] As will be explained furtheron, the windows 60 and 66 indicate the position of the “sweet spot” of the knife sharpener 10. Reference numeral 58 identified an angled, cut away from the section 56 of the housing 53 at the point of entry into the slot 60, while 62 indicates the sidewall that is also referenced as 55 in FIG. 8, which provides improved guidance for the knife being sharpened.

[0027] The newly designed adjustable, flexible bumper arms 46, 48 and positive stop 40 provide the best angles and the necessary pressure for obtaining an even, consistent edge realignment, no matter what sharpening technique is used. These flexible bumper arms 46, 48 add a considerable, additional amount of pressure, over and above what pressure is generated through the flat, stainless steel spring arms 24, 30 above. This is called the “sweet spot” for edge retrieval. This is the area that enables a damaged edge to be reconstructed through the addition of a concentrated force that is generated where the greatest point of leverage is being exerted. The extra force being exerted by these flexible bumper arms 46, 48 spans over an additional ¼ inch on the path downward, toward the “sweet spot” area. The ¼ inch “sweet spot” area most effectively accommodates and captures the greatest variation of knife blade angles which exist on all knife blades within the processing industry. The additional, graduated pressure within the flexible bumper arms traveling within the ¼ inch distance, absorbs any undo shock; and it guarantees that the edge angles will not be damaged, but rather be finessed to capture the greatest variety of edge angles for perfect realignment.

[0028] A square corner stop design, for the flexible bumper arms, has also been incorporated as a feature of this unit. It has been put into a centered position between the flexible bumper arms with a ¼ inch travel distance on each side. It is also nearly perfectly centered with the knife-sharpening slot 60, so that the knife blade angles will be maintained in straight alignment, no matter what sharpening technique is used.

[0029] The flexible bumper arms 46, 48 and the square stop 40 have an additional ¼ inch high-low vertical adjustment specifically suited to a customer's needs. See the groove 42 and fixing bolt 44. These new design elements have been incorporated on the unit to keep all elements of the sharpener in harmony with one another.

[0030] The square bumper stop 40, within the center of the flexible bumper arms, has been positioned to align itself exactly in the center of the sharpening slot, so that when the sharpening rods hit the flexible bumper arms at the same time, both arms will further increase the pressure necessary for a heavy duty edge realignment, and will stop at the same time, at the same point, assuring edge alignment and symmetry. The adjustable, flexible bumper arm unit is preferably made of Teflon, HD poly or UHMW material. This unit is on the backside of the housing unit 53, facing away from the operator, thereby protecting it from operator abuse. Prior art units have their hardware facing toward the operator.

[0031] Other knife sharpening units do not have these capacities. They either stop on a solid rod, as in U.S. Pat. No. 5,478,272, or rely on the pressure of stop points positioned high above on the sharpening rods, to create the necessary force below for edge retrieval. These units produce higher stress levels on the sharpening rods, eventually leading to breakage within the stress points of the rods and damaging the knife blade and the sharpener itself. Both of these sharpeners cannot keep the sharpening rods in consistent alignment at the bottom of the sharpening slot, or cannot be adjusted to the proper angles necessary for reaching a variety of edge angles, or cannot be effectively readjusted to compensate for material fatigue.

[0032] Other knife sharpeners do not have the proper adjustments or design features to keep the knife blade from cutting into the components of their housing units. As a result, it is common for the edges to become further damaged at the bottom point of the sharpening process.

[0033] Referring to FIG. 5, the newly designed tip enhancer device 78 comprises a circular stainless steel cover plate 79 on the front side of the housing unit 53 that supports two specially treated and tempered stainless steel rods 80, 82 which are tack welded to it, forming an “X” pattern, at the best angles for realigning a knife blade's edge. This device 78 has been placed at the bottom of the sharpening slot 60 as a deflecting device to keep the knife blade tip from cutting into the body of the sharpening unit while maintaining the proper angles on the knife blade that have been realigned during the sharpening process. It is usually at the bottom of the sharpening slot, at the end of the sharpening process where the other knife sharpening units cut into the body of the sharpener, damaging the knife blade's edge and the unit itself, and dulling the edge's tip that has just been sharpened. It is for this reason that this unit is called the tip enhancer.

[0034] The tip enhancer unit 78 mounted on the front side of the housing plate will be precisely linked by two bolts that enter through the pre-slotted holes of the tip enhancer, passing through the pre-slotted holes of the housing unit 53 and through the pre-slotted holes of the flexible bumper arm unit 40 mounted-on the backside, affixed with two stainless steel nylon inserted cap nuts. The square corner stop 40 of the flexible bumper arm unit, and the center point of the tip enhancer will always be in direct correlation with each other and the sharpening slot 60. The fact that these units are precisely bolted in place with two bolts, will always keep this unit stationary and in perfect alignment.

[0035] Stainless steel flathead socket cap screws and locknuts are used for all adjustment points on the knife sharpener. These threaded screws and locknuts are inserted through the solid UHMW and/or high-density polyethylene housing unit and are locked into position with a stainless steel locknut that covers over the drilled holes. As a result, no pathogens are able to form within these suspect areas. Quick adjustments on the processing line are more easily achieved using the components within this sharpening unit. The screw lengths are slightly extended by ¼ inch to protect the precise adjustment of the locknut for each component. On competitive units, the locknuts are easily being hit, throwing the components out of adjustment.

[0036] A ½ inch long x ¼0 inch wide viewfinder window slot 60, 66 is strategically placed horizontally on the housing unit for the operator's viewing of the “sweet spot”, which can be identified as being the slots at the bottom of the sharpening unit horizontally positioned on both the right hand and the left hand side of the slot 60. The sharpening rods 12, 14 cross over into an imaginary line between the two slot windows. When the sharpening rods first make contact with the flexible bumper arm adjustment below, this is the top of the viewfinder slot window. As the sharpening rods' cross over points continue down ¼ inch into the “sweet spot” area, they eventually stop at the square corner stop 43, between the flexible bumper arms. It is at this point that the rods are at the bottom of the viewfinder window, visually indicating that the coordinating adjustments are in synch with the “sweet spot”, providing the best edge retrieval. This window is a visual indicator to the operator that the flexible bumper arm unit is in proper coordination with the adjustments of the sharpening rod and spring assembly above. No other sharpening units are believed to have this adjustment.

[0037] The horizontal ½ inch long×¼ inch wide sight alignment setup windows 36, 38 are strategically placed on the right and left hand sides of the sharpening slot's top or initial position. These windows provide an imaginary line crossover point for the rods to be set at their starting position. When the sharpening rods are centered within the sharpening slot, somewhere within the ¼ inch adjustment position of these two windows, this indicates that the proper adjustments have been made on the sharpening rod and spring assembly cams. As the sharpening rods' spring assembly material fatigue, adjustments will have to be made in accordance with the existing fatigue factors. The horizontal slot windows are always a constant guide for bringing adjustments back to their best settings.

[0038] The over-sized, 2 inches high, blind guide wall 55 for knife blade placement is on the right side of the housing unit. It is 2 inches higher than the left wall 56. The 2 inches high blind guide wall offers a liberal amount of surface area 55 for blade placement. This is the starting point for the knife blade to be guided down into the sharpening slot,,without cutting into the housing unit. Other units do not have a blind guide wall as high as this design does. They may have something that is slightly higher on one side compared to the other, but nothing like the massive surface area that is offered for operator ease and convenience. The other units rely on a downward, vertical movement. As a result, these units are cut into, most readily, at the top position of the narrow sharpening slot, because the guide walls they provide are too short, or non-existent, for the operator to successfully deploy the knife blade into a vertical movement, resulting in a hit-and-miss operation. No other units are believed to contain this design feature.

[0039] The universal mounting holes 50, 52 are placed at the bottom of the housing unit to secure the knife sharpening housing unit to its position on the processing line. The reason we use the words “universal mounting holes” is because these holes can accommodate other manufacturers' or end users' mounting hole positions. This will give the end user the potential for easy adoption.

[0040] A knife-sharpening channel 70 (FIG. 3) runs along the total distance of the sharpening slot 60 on the side facing the operator. This is a recessed area that is ½ inch equidistant from each side of the sharpening slot 60 and is ¼ inch deep into the depth of the housing unit's thickness. The purpose of this slot is threefold: it allows for a visible path for the operator to follow; it allows for a deeper insertion of the knife blade edge into the knife sharpening rod area to achieve complete coverage of the knife blade; and/or the depth of the slot keeps the knife handle from hitting the sharpening rod hardware and protects it from undo pressure and physical abuse.

[0041] Unlike other, prior art knife sharpeners that have been made for food processing plants, this new design concept protects all the fragile, sensitive hardware, as well as their critical adjustments. It is for this reason that all critical adjustments and hardware have been placed on the reverse side of the housing unit, away from the operator, and is further stabilized and protected by being mounted on a solid piece of UHMW and/or high-density polyethylene material. Other units do not have the structural strength within the structure of their housing units, or have the protective positioning of the hardware being placed on the reverse side of the housing unit, away from the operator.

[0042] There is no leverage, protection, or strength when all the hardware and adjustments are facing the operator. The rods bend toward the operator, adding more stress and fatigue. The adjustments facing the operator are knocked out of place more easily. This new unit, with the hardware on the backside, brings the rods in towards the housing for support, strength and durability.

[0043] With reference to FIG. 6, a modified pivoting mechanism for the rods 12 and 14 is in a form that substitutes for the spring plates 24, 30 of FIG. 1, respective first and second coil springs 90, 92, the free ends of which are supported in fixing pins 17 b, 19 b, at one end, and in the pivoting blocks 16, 18 by the fixing pins 17 a, 19 a at the other end, as shown. This embodiment does not require the adjusting cams 24, 28 and 32, 34 of FIG. 1, but provides instead, respective cams 13, 15 which pivot around pins 13 a, 15 a, and which can be adjusted to fix the initial crossing position of the rods 12, 14. As further illustrated in FIG. 6, each resilient mechanism assembly can be covered by a plate 86 that is indicated by dotted lines. Further, the bumper arms 46 and 48 of the stop 40 pivot about the undercutting in the material at 46 a, 48 a to create living hinges that provide the appropriate pivoting action, as well as prevention of breakage of the material of the stopper 40 at the point of bending.

[0044] In FIG. 7, each resilience exerting unit for its respective rod 12, 14 is constituted of a torsion spring 96, 98 that includes a loop 97, with the free ends thereof fixed at either the pivoting block 16, 18, at one end, and in a caming device 96 a, 98 a, in which the free ends of the torsion spring 96, 98 is anchored.

[0045] While the units 40 have been described as comprising arms 46,48, the entire unit can be made of a compressible material, which the ends of the rods 12, 14 press against to obtain the functionality of the arms 46, 48.

[0046] Although the present invention has been described in relation to particular embodiments, thereof, many other variations and modifications and other uses will become apparent to those skilled in the art, or to those who work with these units on a daily basis. It is preferred, therefore, that the present invention be limited, not by specific disclosure herein, but only be appended claims. 

What is claimed is:
 1. A blade sharpening apparatus, comprising: a housing plate having a front face and a rear face; a vertically extending slot commencing adjacent a top end of the housing plate and extending toward a bottom end of the housing plate; first and second, pivotably mounted sharpening rods defining therebetween a movable cross-over point that constitutes a sharpening region for a knife blade; a pivoting mechanism for the rods, biasing the cross-over point toward the top end of the housing plate; and a resilient device located adjacent the bottom end of the knife slot and positioned to be engaged by free ends of the rods when the cross-over point of the rods reaches toward a bottom end of the knife slot, the resilient device exerting a force on the rods which resists the force applied to the rods by a knife blade being sharpened.
 2. The apparatus of claim 1, including an adjustment mechanism for the pivoting mechanism that enables setting the cross-over point to coincide with the slot.
 3. The apparatus of claim 1, including a stop member in the path of the movable cross-over point.
 4. The apparatus of claim 3, wherein the stop member and the resilient device are formed as a single integral stop unit.
 5. The apparatus of claim 4, in which the single integrated stop unit comprises a center block which forms the stop member and upwardly protruding left and right bumper arms which constitute the resilient device.
 6. The apparatus of claim 1, in which the position of the integral stop unit is vertically movable on the housing plate.
 7. The apparatus of claim 1, in which the housing plate is made of a material selected from the group consisting of: a solid UHMW material and a high-density polyethylene material.
 8. The apparatus of claim 1, in which the integrated stop unit is made of a material selected from the group consisting of: a solid UHMW material and a high-density polyethylene material.
 9. The apparatus of claim 1, in which the first and second sharpening rods, the pivoting mechanism, and the integral stop unit are mounted on the rear face of the housing plate.
 10. The apparatus of claim 1, including a cover for the pivoting mechanism.
 11. The apparatus of claim 1, in which the pivoting mechanism includes a first pivoting mechanism for the first sharpening rod and a second pivoting mechanism for the second sharpening rod and each pivoting mechanism comprises a pivotable block in which a first end of each sharpening rod is anchored and a respective spring that serves to pivot the block around a pivot point.
 12. The apparatus of claim 11, in which the spring is a coil spring.
 13. The apparatus of claim 11, in which the pivoting mechanism includes caming devices that enable adjusting an initial position of the cross-over point of the rods.
 14. The apparatus of claim 13, in which the caming devices include for each sharpening rod first and second cams which hold tightly therebetween a free end of the spring.
 15. The apparatus of claim 11, in which the spring is a plate spring.
 16. The apparatus of claim 11, in which the spring is a torsion spring.
 17. The apparatus of claim 1, including a first marking that indicate a correct initial location of the cross-over point.
 18. The apparatus of claim 17, in which the first marking comprises first and second windows which straddle the knife slot and are located toward the top end of the housing plate.
 19. The apparatus of claim 1, including a second marking that indicates the position of a sweet spot of the sharpener.
 20. The apparatus of claim 19, in which the second marking comprises first and second windows that straddle the slot and are located adjacent a bottom end of the slot.
 21. The apparatus of claim 1, further including universal mounting holes by which the sharpener can be mounted to a support structure.
 22. The apparatus of claim 1, further including a tip enhancer.
 23. The apparatus of claim 22, in which the tip enhancer comprises a cover plate and two steel rods that are attached to the cover plate, with the steel rods crossing each other to form an approximate “X” shape.
 24. The apparatus of claim 22, wherein the tip enhancer is located on a face of the housing plate opposite to the face on which the integral stop unit is located.
 25. The apparatus of claim 1, further including a high, blind guide wall which is part of the housing plate and which extends at least about 2 inches above the knife slot.
 26. The apparatus of claim 1, further including a channel defined on a front face of the housing plate and straddling the knife slot.
 27. The apparatus of claim 1, in which the apparatus utilizes exclusively flathead screws and locknuts for attaching components to the housing plate mounted so that pathogens are unable to form within cavities in the housing plate. 